minix/commands/file/file.c

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2005-04-21 16:53:53 +02:00
/* file - report on file type. Author: Andy Tanenbaum */
/* Magic number detection changed to look-up table 08-Jan-91 - ajm */
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#define BLOCK_SIZE 1024
#define XBITS 00111 /* rwXrwXrwX (x bits in the mode) */
#define ENGLISH 25 /* cutoff for determining if text is Eng. */
unsigned char buf[BLOCK_SIZE];
struct info {
int execflag; /* 1 == ack executable, 2 == gnu executable,
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* 3 == core, 4 == elf executable */
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unsigned char magic[4]; /* First four bytes of the magic number */
unsigned char mask[4]; /* Mask to apply when matching */
char *description; /* What it means */
} table[] = {
0x00, 0x1f, 0x9d, 0x8d, 0x00, 0xff, 0xff, 0xff, 0x00,
"13-bit compressed file",
0x00, 0x1f, 0x9d, 0x90, 0x00, 0xff, 0xff, 0xff, 0x00,
"16-bit compressed file",
0x00, 0x65, 0xff, 0x00, 0x00, 0xff, 0xff, 0x00, 0x00,
"MINIX-PC bcc archive",
0x00, 0x2c, 0xff, 0x00, 0x00, 0xff, 0xff, 0x00, 0x00,
"ACK object archive",
0x00, 0x65, 0xff, 0x00, 0x00, 0xff, 0xff, 0x00, 0x00,
"MINIX-PC ack archive",
0x00, 0x47, 0x6e, 0x75, 0x20, 0xff, 0xff, 0xff, 0xff,
"MINIX-68k gnu archive",
0x00, 0x21, 0x3c, 0x61, 0x72, 0xff, 0xff, 0xff, 0xff,
"MINIX-PC gnu archive",
0x00, 0x01, 0x02, 0x00, 0x00, 0xff, 0xff, 0x00, 0x00,
"ACK object file",
0x00, 0xa3, 0x86, 0x00, 0x00, 0xff, 0xff, 0x00, 0x00,
"MINIX-PC bcc object file",
0x00, 0x00, 0x00, 0x01, 0x07, 0xff, 0xff, 0xff, 0xff,
"MINIX-68k gnu object file",
0x00, 0x07, 0x01, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff,
"MINIX-PC gnu object file",
0x01, 0x01, 0x03, 0x00, 0x04, 0xff, 0xff, 0x00, 0xff,
"MINIX-PC 16-bit executable",
0x01, 0x01, 0x03, 0x00, 0x10, 0xff, 0xff, 0x00, 0xff,
"MINIX-PC 32-bit executable",
0x01, 0x04, 0x10, 0x03, 0x01, 0xff, 0xff, 0xff, 0xff,
"MINIX-68k old style executable",
0x01, 0x01, 0x03, 0x10, 0x0b, 0xff, 0xff, 0xff, 0xff,
"MINIX-68k new style executable",
0x02, 0x0b, 0x01, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff,
"MINIX-PC 32-bit gnu executable combined I & D space",
0x02, 0x00, 0x00, 0x0b, 0x01, 0xff, 0xff, 0xff, 0xff,
"MINIX-68k gnu executable",
0x03, 0x82, 0x12, 0xC4, 0xC0, 0xff, 0xff, 0xff, 0xff,
"core file",
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0x04, 0x7F, 0x45, 0x4C, 0x46, 0xff, 0xff, 0xff, 0xff,
"ELF executable",
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};
int tabsize = sizeof(table) / sizeof(struct info);
int L_flag;
_PROTOTYPE(int main, (int argc, char **argv));
_PROTOTYPE(void file, (char *name));
_PROTOTYPE(void do_strip, (int type));
_PROTOTYPE(void usage, (void));
int main(argc, argv)
int argc;
char *argv[];
{
/* This program uses some heuristics to try to guess about a file type by
* looking at its contents.
*/
int c, i;
L_flag= 0;
while ((c= getopt(argc, argv, "L?")) != -1)
{
switch(c)
{
case 'L':
L_flag= 1;
break;
case '?':
usage();
default:
fprintf(stderr, "file: panic getopt failed\n");
exit(1);
}
}
if (optind >= argc) usage();
for (i = optind; i < argc; i++) file(argv[i]);
return(0);
}
void file(name)
char *name;
{
int i, fd, n, mode, nonascii, special, funnypct, etaoins;
int j;
long engpct;
int c;
struct stat st_buf;
printf("%s: ", name);
#ifdef S_IFLNK
if (!L_flag)
n = lstat(name, &st_buf);
else
n = stat(name, &st_buf);
#else
n = stat(name, &st_buf);
#endif
if (n < 0) {
printf("cannot stat\n");
return;
}
mode = st_buf.st_mode;
/* Check for directories and special files. */
if (S_ISDIR(mode)) {
printf("directory\n");
return;
}
if (S_ISCHR(mode)) {
printf("character special file\n");
return;
}
if (S_ISBLK(mode)) {
printf("block special file\n");
return;
}
if (S_ISFIFO(mode)) {
printf("named pipe\n");
return;
}
#ifdef S_IFLNK
if (S_ISLNK(mode)) {
n= readlink(name, (char *)buf, BLOCK_SIZE);
if (n == -1)
printf("cannot readlink\n");
else
printf("symbolic link to %.*s\n", n, buf);
return;
}
#endif
if (!S_ISREG(mode)) {
printf("strange file type %5o\n", mode);
return;
}
/* Open the file, stat it, and read in 1 block. */
fd = open(name, O_RDONLY);
if (fd < 0) {
printf("cannot open\n");
return;
}
n = read(fd, (char *)buf, BLOCK_SIZE);
if (n < 0) {
printf("cannot read\n");
close(fd);
return;
}
if (n == 0) { /* must check this, for loop will fail otherwise !! */
printf("empty file\n");
close(fd);
return;
}
for (i = 0; i < tabsize; i++) {
for (j = 0; j < 4; j++)
if ((buf[j] & table[i].mask[j]) != table[i].magic[j])
break;
if (j == 4) {
printf("%s", table[i].description);
do_strip(table[i].execflag);
close(fd);
return;
}
}
/* Check to see if file is a shell script. */
if (mode & XBITS) {
/* Not a binary, but executable. Probably a shell script. */
printf("shell script\n");
close(fd);
return;
}
/* Check for ASCII data and certain punctuation. */
nonascii = 0;
special = 0;
etaoins = 0;
for (i = 0; i < n; i++) {
c = buf[i];
if (c & 0200) nonascii++;
if (c == ';' || c == '{' || c == '}' || c == '#') special++;
if (c == '*' || c == '<' || c == '>' || c == '/') special++;
if (c >= 'A' && c <= 'Z') c = c - 'A' + 'a';
if (c == 'e' || c == 't' || c == 'a' || c == 'o') etaoins++;
if (c == 'i' || c == 'n' || c == 's') etaoins++;
}
if (nonascii == 0) {
/* File only contains ASCII characters. Continue processing. */
funnypct = 100 * special / n;
engpct = 100L * (long) etaoins / n;
if (funnypct > 1) {
printf("C program\n");
} else {
if (engpct > (long) ENGLISH)
printf("English text\n");
else
printf("ASCII text\n");
}
close(fd);
return;
}
/* Give up. Call it data. */
printf("data\n");
close(fd);
return;
}
void do_strip(type)
int type;
{
if (type == 1) { /* Non-GNU executable */
if (buf[2] & 1)
printf(", UZP");
if (buf[2] & 2)
printf(", PAL");
if (buf[2] & 4)
printf(", NSYM");
if (buf[2] & 0x20)
printf(", sep I&D");
else
printf(", comm I&D");
if (( buf[28] | buf[29] | buf[30] | buf[31]) != 0)
printf(" not stripped\n");
else
printf(" stripped\n");
return;
}
if (type == 2) { /* GNU format executable */
if ((buf[16] | buf[17] | buf[18] | buf[19]) != 0)
printf(" not stripped\n");
else
printf(" stripped\n");
return;
}
if (type == 3) { /* Core file in <sys/core.h> format */
switch(buf[36] & 0xff)
{
case 1: printf(" of i86 executable"); break;
case 2: printf(" of i386 executable"); break;
default:printf(" of unknown executable"); break;
}
printf(" '%.32s'\n", buf+4);
return;
}
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if (type == 4) { /* ELF executable */
printf("\n");
return;
}
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printf("\n"); /* Not an executable file */
}
void usage()
{
printf("Usage: file [-L] name ...\n");
exit(1);
}